Vulcanization of rubber



" 5 used in vulcanization.

Amongthe peroxides, which I have found Patented Febi 10, 1931 A c'oRronA'rmmornEw YORK I VULCAISI IZA IQNV or} R BER Y No. Drawing.

This invention relates to improvementsin the vulcanization of rubber and includes. a new method of vulcanization and a newruber composition. p

V :In the, compoundingrand mixing:'ofjliubher it is customary tobreakdown the'rubber v on the rubbermillarid .to ivorkthe ;com,-*

poundi gingredientsinto the u ae the mill. Thebreaking vdown and compounding of'the rubber is accompaniedyvith considerable self-heatingin addition to'the heating a of the rubber mix by the heated compounding rolls.

, In the compounding and; mixing of rub ber containing the more active orgamc accelerators,.and particularlyithoseaccelerators known ;,as. ultra-accelerators, -trouble 1s frequently encountered and lossiis frequently incurred from s-the fs corching?" -of a comf 7 pound or premature :vulcanization 5; thereof duringand-aftermilling; In some cases pre-' cautions are taken to reducethe danger of scorching, or premature vulcanizatlon by coolingthe rubberlduring' compounding or immediatelyafter compoundilig- 'i'aThe present iinvention provides anf, improved process in which the danger of scorch; ing or. premature vulcanizationrlslehminate'd or minimized, anl. in which eveirultra-accelerators maybe.employedlwithouuwrlanger of scorching or premature vulcanization.

I'The [present :invention is? based upon the discovery Qthat, bytlie addition of a small percentage, of a suitable peroxide, and par- I ticularly of a non-aci'dicfperoxide of a metal,

sucha's lead peroxide; to a rubber. compound containing an ultra-accelerator; the tendency to cure ori-vulcanize below temperatures corresponding to about 20 pounds steam pressure is eliminated or greatly reduced with out, rhovjvever, appreciably prolong ng; the

time ;requi re'd for satisfactoryvulcanization at- :higher temperatures corresporidingto; the

higher'steam pressures which are commonly toibe particularly valuable is. lead, peroxide,

PbO2- uNom ciper desiofcertainother metals :exert an action similar to that of lead; p r xi e ut. in varying, degrees. Among Application ,filed December 30,1927. {se ial 110.. 243,777." 7

suchoth'er metal peroxidesmay begmentioned the dioxides of alkaline earth metals e. g1,

calcium, strontium, and barium. Barium peroxide is a valuable; peroxide for use Where White or light colored goods are desired. 1

The amount of the peroxide which it is necessary to add to obtain the V desired elimination or reduction of danger of {scorching is'sinall' .In some cases as smallan amount: as'o'ne-quarterrofone percent or less'of lead peroxide based onthe rubber, i's s'uflicient,

While in lother cases around one'percent of 7 lead peroxide based ion the rubber, gives ex-' cellent results The amount illvary with the partlcularperoxide employed and tosome extent with the nature of the mix and particularly the nature of the accelerator or accelerators employed. In the case of barium peroxide, for example, aroun'd one percent based on the rubber hasbeen found-satisfactory with certainsupereaccelerators.

'V /Vhile I do not desire-to limit myself by loivtemperaturesand which would otherwise initiate or bring about scorching or .pre-v "vulcanization. The. actioncof tlIQ P B-IOXlidGS. moreover seems to beconfined. to their re tardmgor preventing of vulcanizationat low temperature since, at highertemperatures,

commonly used in vulcanizatiomwthe vulcanlzatlon takes'place readilyeandi does not appearto be appreciably prolonged. Theiaddition of the. peroxide. moreover has: no 1 apthe aging or' the vulcanized compounds.

Themore actl'veiorganic accelerators wliich cause or tend to cause scorchmg'or premature vulcanization include ultraaccelerators,

and the more active accelerators.which are not commonly referred toas' ultra-acceleracorresponding to the-higher steam ,lpressures tors. Among such accelerators may I be a mentioned-captax 1 (mereaptobenz othiazole) wads (t reme hylthiummdisulfide) ,;z1mace so preciabl'y' orseriouslyldeleterious'effecton.

. forty poundssteam pressure. The results (zinc dimethyldithiocarbamate), etc. Such accelerators may be used alone or in various admixtures. 1 V 7 The present inventionis of more or less general application to the-vulcanization of different rubber compounds containing various compounding materials such as zinc oxide, finely divided carbon, Whiting, etc. 1111001115 cases-acids such as :stear i'c aci'd are ad-vantageous andiin other case'santi-oxidantssuch as agerite resin (the condensationproduct of aldol and alphanaphthylamine) "Canadvanta eously be. employed, v n

In the practice of the inventionfthe "iiigredients of the rubber mix orconipound can be compounded in the ordinary Way- 0111.110

rubber rollsbut with incorporation of the peroxide in the rubber min so that 1t is present during tne nnllingoperation and in the 20 milled product. the perox de The rubber mix containing a stabilized rubber mix, and,

even thoug it maybe heatedto some extent 0 Pt the invention. In these examples, the accelerators employed are referred to by their trade name, for convenience, and-agerite is also referred to by its trade name, the chemical nature of these materials being indicated above.

In the following examples, the abbreviation U. C. is used to indicate an uncured compound, While poor cure is used to indicate an undercured compound. In each e: ample 'the compound employed is given both without the addition of the metal peroxide and with tllefidClItlOIl of such peroxide in amount indicated, thus giving a direct comparisono't the compounds containing the peroxide "ith the blank from Which the peroxide is absent.

Following the compounds aretables showing for each compound the time and steam pressure to which it'is subjected and the tensile strength and elongation I of the proeuct so treated. 1 Thus at the top of each column the expressionstfi at means that the rubber compound is heated for five minutes to a temperature corresponding to ten poundssteam pressure. Similarly, theheading at 4-0 indicates vulcanization for twenty minutes at obtained are those obtained with test slabs of "specie preczmtions are taken.

the kind commonly employed in rubber laboratories for testing and control purposes.

I The figures in each column indicate first the tensile strength andthen the elongation, in

accordance with customary practice indicat-v 111g011 1501115507 testing rubber compounds.

The following example gives the results obtained with the use'o-i captax (mercaptobenzothiazole) as an accelerator. This accelerator 'is'fnot. commonly, considered an ultra-accelerator, but it is one which tends to causes'corchiug or .prevulcanization.unless V .110 pound employed and the results obtained are 1naccordancewith the above PXPll-llitillOll.

Pele crepe (rubber).'- 100 100 100 Zinc 0xide 5 5' l 5 Quaker whiting. 50 50 50, s 11 4 4 y 4 5 010 ,satlo 1011510 1510010 00mm cure U. C. 2120-810 2700-790 2720-780 3440-770 3320-740I 5 06 00 10 at 00 15 at Tlhe renewing example gives 011 5 11115 obtained with' an ultra-accelerator I 131 ads or tetramethylthiuramdisulfide) A A1 A2 Pale crepe (rubber) .l 100 100 100 H Zinc oxide 5 1 5- 5 Quaker whiting 50; 50 5O lph 4 4 4 3 10 1 3 10 3 10 45at2%60'at2% 5 1010 102110 301 010 1 2000-730 3520755 37 10705 U. C. 800-720, U20."

com-

300i 2% 45 at 21 2 00 312 30040 5 040 IQat lO 200040 aoauo 311600 is at 00 water) i5at60 From the foregoingenample's, which illustion which can be kept and stored Without the necessity of cooling it to a low temperae ture andwithout danger of self-vulcanization during storage. 2

.Iclaim:+- 7.. p v v 1. The improvement in the v lcanization of rubber with the aid of an active accelerator Whichc'omp'rises incorporating in the rubber compound a small amount of a peroxide'hav: ing the property of preventing or retarding scorching 0r prevulcanization of. the rubber compound. v V Y 2; The improvement in the vulcanization of rubber With the aid of an'active accelerator which comprises incorporating in the rubber compound a small amount of a metal peroxide having the property of preventing or retarding scorching or prevulcanization' of the rubber 'compound. .7 Y

3.- The improvement in; the prevention or retarding'of scorching or pervulcanization of rubber compounds containingnan active accelerator Which comprises incorporating in the rubber compound a small amount of lead peroxide, 4. An unvulcanized rubber compound con tainingan active accelerator and a's'mall amount of azper oxide having the property of preventing or retarding scorching or prevulcanization of-the compound during the milling'and'subsequent storage of the unvulcan ized compound.

5, An unvulcanized rubber compound c011- taini ng an activeaccelerator and a small amount of a metalperoxide having the property of preventing or retardmgseo'rchmg or prevulcanization of the compound during at inning aabis aa storage 00110011 vulcanized compound." v 6. Anunvulcanized rubbercompound containing' an active accelerator, 'saidcompoun d being stabilizedagainst scorching or prevulcanization by, the addition of-a small amount of lead peroxide. W

'TIThe improvement in the prevention or retarding of scorching or prevulcaniza'tion of rubber compoundsfc'ontainingianactive-accelerator which comprises incorporating the rubber compound a small amount of a barium peroxide. i

taining an active accelerator, said compound beingistabilizedagainst scorching or pre-vulcanization bythe addition offa small amount of barium peroxide.

In testimony whereof I afiix my signature. 2 r v J: ALBERT A. SOMERVILLE;

8. An unvulcanized rubber compound con 

